Omegamon introduced a new user interface based on JAVA. This a PC/UNIX interface.
You cannot use TPX to access the Omegamon interface that is based on Java. This a PC/UNIX interface.
However, Omegamon still allows logons via the old 3270 interface. You can logon from TPX this way.
This says explicitly:
Current OMEGAMON users can continue to use the familiar 3270 interfaces, since both the OMEGAMON Classic and OMEGAMON II monitors are included with the OMEGAMON XE solutions.